Aligned multiple emitter package

ABSTRACT

A multiple element emitter package is disclosed for increasing color fidelity and heat dissipation, improving current control, increasing rigidity of the package assembly. In one embodiment, the package comprises a surface-mount device a casing with a cavity extending into the interior of the casing from a first main surface is provided. A lead frame is at least partially encased by the casing, the lead frame comprising a plurality of electrically conductive parts carrying a linear array of light emitting devices (LEDs). Electrically conductive parts, separate from parts carrying the LEDs have a connection pad, wherein the LEDs are electrically coupled to a connection pad, such as by a wire bond. This lead frame arrangement allows for a respective electrical signal can be applied to each of the LEDs. The emitter package may be substantially waterproof, and an array of the emitter packages may be used in an LED display such as an indoor and/or outdoor LED screen.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to multi emitter packages, andmore particularly to surface mount packages having multiple emittersthat are aligned to improve emission uniformity.

2. Description of the Related Art

In recent years, there have been dramatic improvements in light emittingdiode (LED) technology such that LEDs of increased brightness and colorfidelity have been introduced. Due to these improved LEDs and improvedimage processing technology, large format, full color LED video screenshave become available and are now in common use. Large format LEDdisplays typically comprise a combination of individual LED panelsproviding image resolutions determined by the distance between adjacentpixels or “pixel pitch”.

Outdoor display that may be intended for viewing from greater distances,can have relatively large pixel pitches and usually comprise discreteLED arrays. In the discrete LED arrays, a cluster of individuallymounted red, green, and blue LEDs are driven to form what appears to theviewer as a full color pixel. On the other hand, indoor screens, whichrequire shorter pixel pitches such as 3 mm or less, can comprise panelshaving a plurality of surface mount devices (SMD or SMDs) or other typesof emitter packages, each of which defines a pixel. Each emitter packagecan carry red, green, and blue emitting LEDs whose emitted lightcombines to generate the desired wavelength or color of light.

Both indoor and outdoor displays are typically viewable across asubstantial range of off-axis angles, such as up to 145° or evengreater. The LEDs in some conventional emitter packages suffer fromdifferent emission characteristics at different viewing angles. The LEDsin these packages can be arranged in a cluster at or near the center ofthe package, and at different viewing angles the particular LED closestto the viewer may emit more prominently. For example, if the packagewere viewed at an angle such that the red LED was closest to the viewer,the red may emit more prominently than when the package is vieweddirectly. The same could be true for the blue and green LEDs. As aresult, the color generated by the packages can be perceived asdifferent depending on the viewing angle.

Conventional emitter packages can also suffer from a perceptible loss ofcolor fidelity with increasing viewing angle. Additionally, the materialof each emitter package and/or the material used to mount each of theLEDs within the packages may have reflective characteristics, which canfurther decrease color fidelity by creating unwanted light reflectionand/or glare.

Emitter packages such as SMDs, whether containing integrated circuits ordiscrete components such as diodes or power transistors, can generatesignificant heat, particularly in high power devices. This heattypically needs to be dissipated to prevent premature componentdegradation or failure. This can require additional thermal managementcomponent to dissipate sufficient heat to maintain the operatingtemperature of the active circuit or junction side of the componentbelow a target temperature (for example, 110° C. or below). Variousthermal management strategies including conduction heat transfer are incommon use. One conventional way of implementing conduction heattransfer for dissipating heat in an electronic package is to allow theheat to conduct away along the leads of the device. However, the leadsoften do not have sufficient mass or exposed surface area to provideeffective heat dissipation. For example, high intensity LEDs that emitlight principally in the visible part of the electromagnetic spectrumcan generate significant amounts of heat that is difficult to dissipateusing such conventional techniques.

SUMMARY OF THE INVENTION

The present invention provides emitter package lead frames, emitterpackages and LED screens that provide for improved color emissionuniformity at different viewing angles. The present invention alsoprovides emitter packages with that allow for improved current controlof the emitters in the packages, rigidity of the package assembly, andwaterproof package operation.

One embodiment of an electrically conductive lead frame for a multipleemitter package comprising a plurality of electrically conductivecathode parts each having an attach pad for carrying at least one lightemitting device with each attach pad electrically coupled to its atleast one light emitting device. A corresponding plurality ofelectrically conductive anode parts are included separate from each thecathode parts, each of said anode parts having a connection pad arrangedto allow electrical connection to a light emitting device. Wherein theattach pads and connection pads are arranged to hold light emittingdevices in linear alignment.

One embodiment of an emitter package according to the present inventioncomprises a casing having a cavity extending into the interior of thecasing from the casing's top surface. A lead frame is included that isintegral to the casing with the lead frame comprising conductive partsholding a plurality of light emitting devices in linear alignment andemitting out said cavity. The lead frame also allows for an electricalsignal to be applied to the light emitting devices through the leadframe.

One embodiment of a light emitting device display according to thepresent invention comprises a substrate carrying an array of emitterpackages. Each of the emitter packages comprises a casing and containslinearly aligned light emitting devices. Electrically connected drivecircuitry is included to selectively energize the array of emitterpackages for producing visual images on said display.

These and other further features and advantages of the invention wouldbe apparent to those skilled in the art from the following detaileddescription, taken together with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a surface mount device according to thepresent invention;

FIG. 2 is a top plan view of the embodiment shown in FIG. 1;

FIG. 3 is a sectional view of the embodiment of FIG. 1 as seen along theline 3-3 in FIG. 2;

FIG. 4 is a bottom view of the embodiment shown in FIG. 1;

FIG. 5 is a left side elevation view of the embodiment shown in FIG. 1,with the right side being substantially similar;

FIG. 6 is a front side elevation view of the embodiment shown in FIG. 1,with the back side being substantially similar;

FIG. 7 is a perspective view of a lead frame in accordance with oneembodiment that may be used in the device of FIG. 1;

FIG. 8 is a side elevation view of the lead frame shown in FIG. 7;

FIG. 9 is a sectional view of a lead frame in FIG. 8 taken along sectionlines 9-9 and showing a lead frame through hole;

FIG. 10 is a sectional view of a lead frame in FIG. 8 taken alongsection lines 10-10 and showing lead frame V-cuts;

FIG. 11 is a sectional view, along the lines of that shown in FIG. 3, ofanother embodiment of a surface mount device according to the presentinvention;

FIG. 12 is a bottom view of the embodiment shown in FIG. 11;

FIG. 13 is an end elevation view of the embodiment shown in FIG. 11;

FIG. 14 is a top dimensional view of one embodiment of a surface mountdevice according to the present invention;

FIG. 15 is a front side elevation view of the embodiment shown in FIG.1, with the back side view being substantially similar;

FIG. 16 is a front side dimensional view of the embodiment shown in FIG.15; and

FIG. 17 is a front elevation view of a portion of an LED display screenincorporating surface mount devices in accordance with embodiments ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides structures for multi emitter packagesthat allow the packages to emit light with improved color uniformity atdifferent viewing by linearly aligning the emitters within the package.In one embodiment, the emitters are vertically aligned although it isunderstood that in different applications the emitters could behorizontally aligned or aligned at an angle. In some embodiments, thepackages can also have lead frame structures that allow each of theemitters in the package to be driven by its own electrical signal. Thisallows for improved control over the color and intensity of lightemitted by the emitter package.

In one embodiment of an emitter package according to the presentinvention the emitters can comprise red, green and blue emitters thatare vertically aligned at or near the centerline of the package so thatthe viewing angles of the red, green and blue colors coincide with eachother. This allows the color of the emitter package to appear moreuniform at different viewing angles compared to prior art packageshaving emitters in a cluster. The emitter packages according to thepresent invention can also comprise a lead frame and casing that helpskeep the package waterproof, and also comprises features to improvepackage rigidity, such as through holes.

The present invention is applicable to different types of emitterpackages such as surface mount devices (SMDs) that can be used in manydifferent lighting applications such as LED color screens or decorativelighting and applications where waterproof devices are desired.Different embodiments of emitter packages are described below thatutilize light emitting diodes as their emitters, but it is understoodthat other emitter package embodiments can use different types ofemitters.

It will be understood that when an element is referred to as being “on”,“connected to”, “coupled to” or “in contact with” another element, itcan be directly on, connected or coupled to, or in contact with theother element or intervening elements may be present. In contrast, whenan element is referred to as being “directly on,” “directly connectedto”, “directly coupled to” or “directly in contact with” anotherelement, there are no intervening elements present. Likewise, when afirst element is referred to as being “in electrical contact with” or“electrically coupled to” a second element, there is an electrical paththat permits current flow between the first element and the secondelement. The electrical path may include capacitors, coupled inductors,and/or other elements that permit current flow even without directcontact between conductive elements.

Although the terms first, second, etc. may be used herein to describevarious elements, components, regions, and/or sections, these elements,components, regions, and/or sections should not be limited by theseterms. These terms are only used to distinguish one element, component,region, or section from another element, component, region, or section.Thus, a first element, component, region, or section discussed belowcould be termed a second element, component, region, or section withoutdeparting from the teachings of the present invention.

Embodiments of the invention are described herein with reference tocross-sectional view illustrations that are schematic illustrations ofembodiments of the invention. As such, the actual thickness ofcomponents can be different, and variations from the shapes of theillustrations as a result, for example, of manufacturing techniquesand/or tolerances are expected. Embodiments of the invention should notbe construed as limited to the particular shapes of the regionsillustrated herein but are to include deviations in shapes that result,for example, from manufacturing. A region illustrated or described assquare or rectangular will typically have rounded or curved features dueto normal manufacturing tolerances. Thus, the regions illustrated in thefigures are schematic in nature and their shapes are not intended toillustrate the precise shape of a region of a device and are notintended to limit the scope of the invention.

The following description presents preferred embodiments. Thisdescription is not to be taken in a limiting sense but is made merelyfor the purpose of describing the general principles of the invention,the scope of which is further understood by the appended claims.

FIGS. 1-8 show one embodiment of a multiple emitter package 10 accordingto the present invention that comprises a surface-mount device (SMD) 10.As mentioned above, it is understood that the present invention can beused with other types of emitter packages beyond SMDs. The package 10comprises a casing 12 that carries an integral lead frame 14. The leadframe 14 comprising a plurality of electrically conductive connectionparts used to conduct an electrical signals to the package's lightemitters, and to also assist in dissipating heat generated by theemitters.

The lead frame 14 can be arranged in many different ways and differentnumbers of parts can be utilized in different package embodiments. Thepackage 10 is described below utilizing three emitters, and in theembodiment shown, the lead frame is arranged so that each of theemitters is driven by a respective electrical signal. Accordingly thereare six conductive parts in the embodiment shown, comprising a pair ofconductive parts for each emitter with an electrical signal applied toeach of the emitters through its conductive part pair. For the package10, the conductive parts comprise first, second and third anode parts16, 18, 20, and first, second and third cathode parts 22, 24, 26 (bestshown in FIG. 7) each having an emitter attach pad.

The casing 12 can have many different shapes and sizes and in theembodiment shown is generally square or rectangular, with upper andlower surfaces 28 and 30, side surfaces 32 and 34 and end surfaces 36and 38. The upper portion of the casing further comprises a recess orcavity 40 extending from the upper surface 28 into the body of thecasing 12 to the lead frame 14. Emitters are arranged on the lead framesuch that light from the emitters emits from the package 10 through thecavity 40. In some embodiments, a reflective insert or ring 42 (shown inFIGS. 1-3) may be positioned and secured along at least a portion of aside or wall 44 of the cavity 40. The effectiveness of the reflectivityof the ring 42 and the emission angle of the package can be enhanced bytapering the cavity 40 and ring 42 carried therein inwardly toward theinterior of the casing. By way of example and not by limitation and asbest shown in FIG. 15, a reflector angle 46 of ˜50 degrees provides fora suitable reflectivity and viewing angle.

In some embodiments, the cavity 40 may be at least partially filled witha fill material 48 that can protect and positionally stabilize the leadframe 14 and the emitters carried thereby. In some instances, the fillmaterial 48 may cover the emitters and the portions of the lead frame 14exposed through the cavity 40. The fill material 48 may be selected tohave predetermined optical properties so as to enhance the projection oflight from the LEDs, and in some embodiments is substantiallytransparent to the light emitted by the package's emitters. The fillmaterial 48 can also be shaped, such as hemispheric or bullet shaped, orthe fill material can be fully or partially concave in the cavity 40.The fill material 48 may be formed from a resin, an epoxy, athermoplastic polycondensate, glass, and/or other suitable materials orcombinations of materials. In some embodiments, materials may be addedto the fill material 48 to enhance the emission, absorption and/ordispersion of light to and/or from the LEDs.

The casing 12 may be fabricated of material that is preferably bothelectrically insulating and thermally conductive. Such materials arewell-known in the art and may include, without limitation, certainceramics, resins, epoxies, thermoplastic polycondensates (e.g., apolyphthalamide (PPA)), and glass. In a preferred embodiment, the casing12 may be formed of dark or black ceramic material(s) as they have beenfound to improve contrast in image generation SMD packages, such as withSMDs employed in video displays. The package 10 and its casing 12 may beformed and/or assembled through any one of a variety of known methods asis known in the art. For example, the casing 12 may be formed or moldedaround the anode parts 16, 18, 20 and cathode parts 22, 24, 26, such asby injection molding. Alternatively, the casing may be formed insections, for example, top and bottom sections with the anode parts 16,18, 20 and cathode parts 22, 24, 26 formed on the bottom section. Thetop and bottom sections can then be bonded together using know methodsand materials, such as by an epoxy, adhesive or other suitable joindermaterial.

In the illustrative embodiment depicted, the package 10 utilizes first,second and third LEDs 50, 52, 54, each of which can emit the same colorof light or different color of light than the others. In the embodimentshown, the LEDs 50, 52, 54 emit blue, green and red colors,respectively, so that when appropriately energized the LEDs produce incombination a substantially full range of colors. Further, whenappropriately energized, the LEDs 50, 52, 54 emit a white lightcombination of different color temperatures.

LED structures, features, and their fabrication and operation aregenerally known in the art and only briefly discussed herein. LEDs canhave many different semiconductor layers arranged in different ways andcan emit different colors. The layers of the LEDs can be fabricatedusing known processes, with a suitable process being fabrication usingmetal organic chemical vapor deposition (MOCVD). The layers of the LEDchips generally comprise an active layer/region sandwiched between firstand second oppositely doped epitaxial layers, all of which are formedsuccessively on a growth substrate or wafer. LED chips formed on a wafercan be singulated and used in different application, such as mounting ina package. It is understood that the growth substrate/wafer can remainas part of the final singulated LED or the growth substrate can be fullyor partially removed.

It is also understood that additional layers and elements can also beincluded in the LEDs, including but not limited to buffer, nucleation,contact and current spreading layers as well as light extraction layersand elements. The active region can comprise single quantum well (SQW),multiple quantum well (MQW), double heterostructure or super latticestructures.

The active region and doped layers may be fabricated from differentmaterial systems, with one such system being Group-III nitride basedmaterial systems. Group-III nitrides refer to those semiconductorcompounds formed between nitrogen and the elements in the Group III ofthe periodic table, usually aluminum (Al), gallium (Ga), and indium(In). The term also refers to ternary and quaternary compounds such asaluminum gallium nitride (AlGaN) and aluminum indium gallium nitride(AlInGaN). In a preferred embodiment, the doped layers are galliumnitride (GaN) and the active region is InGaN. In alternative embodimentsthe doped layers may be AlGaN, aluminum gallium arsenide (AlGaAs) oraluminum gallium indium arsenide phosphide (AlGaInAsP) or aluminumindium gallium phosphide (AlInGaP) or zinc oxide (ZnO).

The growth substrate/wafer can be made of many materials such assilicon, glass, sapphire, silicon carbide, aluminum nitride (AlN),gallium nitride (GaN), with a suitable substrate being a 4H polytype ofsilicon carbide, although other silicon carbide polytypes can also beused including 3C, 6H and 15R polytypes. Silicon carbide has certainadvantages, such as a closer crystal lattice match to Group III nitridesthan sapphire and results in Group III nitride films of higher quality.Silicon carbide also has a very high thermal conductivity so that thetotal output power of Group-III nitride devices on silicon carbide isnot limited by the thermal dissipation of the substrate (as may be thecase with some devices formed on sapphire). SiC substrates are availablefrom Cree Research, Inc., of Durham, N.C. and methods for producing themare set forth in the scientific literature as well as in a U.S. Pat.Nos. Re. 34,861; 4,946,547; and 5,200,022.

LEDs can also comprise additional features such as conductive currentspreading structures, current spreading layers, and wire bond pads, allof which can be made of known materials deposited using known methods.Some or all of the LEDs can be coated with one or more phosphors, withthe phosphors absorbing at least some of the LED light and emitting adifferent wavelength of light such that the LED emits a combination oflight from the LED and the phosphor. LED chips can be coated with aphosphor using many different methods, with one suitable method beingdescribed in U.S. patent application Ser. Nos. 11/656,759 and11/899,790, both entitled “Wafer Level Phosphor Coating Method andDevices Fabricated Utilizing Method”, and both of which are incorporatedherein by reference. Alternatively the LEDs can be coated using othermethods such as electrophoretic deposition (EPD), with a suitable EPDmethod described in U.S. patent application Ser. No. 11/473,089 entitled“Close Loop Electrophoretic Deposition of Semiconductor Devices”, whichis also incorporated herein by reference. Furthermore, LEDs may havevertical or lateral geometry as is known in the art. Those comprising avertical geometry may have a first contact on a substrate and a secondcontact on a p-type layer. An electrical signal applied to the firstcontact spreads into the n-type layer and a signal applied to the secondcontact spreads into a p-type layer. In the case of Group-III nitridedevices, it is well known that a thin semitransparent typically coverssome or the entire p-type layer. It is understood that the secondcontact can include such a layer, which is typically a metal such asplatinum (Pt) or a transparent conductive oxide such as indium tin oxide(ITO).

LEDs may also comprise a lateral geometry, wherein both contacts are onthe top of the LEDs. A portion of the p-type layer and active region isremoved, such as by etching, to expose a contact mesa on the n-typelayer. A second lateral n-type contact is provided on the mesa of then-type layer. The contacts can comprise known materials deposited usingknown deposition techniques.

In the illustrative embodiment shown, the lead frame's anode and cathodeparts 16, 18, 20, 22, 24, 26 project outwardly through the opposedsurfaces 36 and 38 of the casing 12. As best shown in FIG. 4, anodeparts 16, 18, 20 extend from surface 36, and cathode parts 22, 24, 26extend from surface 38. The anode and cathode parts are arranged tooperate in pairs to conduct an electrical signal to their respectivelight emitter when the package 10 is surface mounted for operation. Inthe embodiment shown, the anode and cathode parts 16, 18, 20, 22, 24, 26are bent orthogonally to extend outside of and down along their endsurfaces 36 and 38 of the casing, then bent orthogonally again to formend portions 82, 84, 86, 88, 90, 92 that extend along the lower surface30 of the casing 12. The outwardly facing surfaces of the end portions82, 84, 86, 88, 90, 92 of the leads are substantially flush tofacilitate connection to an underlying substrate. As best shown in FIG.3, the end portions 82, 84, 86, 88, 90, 92 (with only end portions 86,88 being visible) of the leads can electrically connected or bonded totraces or pads on the substrate 94 using any of a number of well-knownconnection techniques, including soldering. It is understood that inother embodiments all or some of the end portions 82, 84, 86, 88, 90, 92can be bent in an opposite direction while still allowing for surfacemounting.

The cathode parts 22, 24, 26 comprise central surfaces or mounting pads68, 70, 72 for carrying the LED chips 50, 52, 54 in a linear array thatextends in a direction 74 perpendicular to the side surfaces 32 and 34,with the LEDs 50, 52, 54 being aligned generally along a central axis ofthe casing 12. This alignment allows for improved color uniformity atdifferent viewing angles compared to packages having LEDs arranged inother ways, such as in a cluster.

Mounting pads 68 and 78 extend toward the center of the casing 12, whichallows for the LEDs 50, 54 to be mounted closer to the center of thecasing 12 so that they can emit out of the cavity 40. The anode parts16, 18, 20 include electrical connection pads 76, 78, 80, respectively,positioned adjacent to, but spaced apart from, the mounting pads 68, 70,72. Connection pads 76 and 80 extend toward the center of the casing 12to allow for electrical connection to LED 50, 54 that are mounted closerto the center of the casing 12 by extensions of mounting pads 68, 70.

The anode parts 16, 18, 20 run generally parallel to one another andcathode parts 22, 24, 26 run generally parallel to one another other,with all extending in a direction perpendicular to the direction 74 ofthe linear LED array. The leads can have different widths and can besmall enough that when the package 10 is viewed from the top, they areminimally visible or not visible. Additionally and/or alternatively, theleads may be obstructed from view from the top by the casing 12. As bestseen in FIGS. 1 and 2, the cavity 40 extends into the casing interior asufficient depth to expose the attach and connection pads 68, 70, 72,76, 78, 80. In a preferred embodiment, each of the LEDs 50, 52, 54 hasits own pair of contacts or electrodes arranged so that when anelectrical signal is applied across the contacts the LED emits light.The contacts of the LEDs are electrically connected to an anode andcathode part pair. Ensuring that each of the LEDs 50, 52, 54 has its owncathode and anode pair is advantageous for many reasons, such asproviding easier electrical control of each LED. In accordance with atypical implementation of the embodiments shown, one of the contacts ofLEDs 50, 52, 54 is coupled to the chip carrier pads 68, 70, 72 while theother of LED contacts is coupled, respectively, to the pads 76, 78, 80.Different known structures and methods can be used for making thisconnection, with one such structure being wire bonds 95, 97, 99 appliedusing known methods.

The anode parts 16, 18, 20 and cathode parts 22, 24, 26 may be made froman electrically conductive metal or metal alloy, such as copper, acopper alloy, and/or other suitable low resistivity, corrosion resistantmaterials or combinations of materials. As noted, the thermalconductivity of the leads may assist, to some extent, in conducting heataway from the LEDs 50, 52, 54 carried by the SMD as shown by the arrow98. As best shown in FIG. 7, to further assist in thermal dissipationthe anode part 18 and cathode part 24 can comprise an enlarged portionnear casing's edge. These enlarged portions provide increased surfacearea to spread the heat generated by the LEDs 50, 52, 54.

Each of the LEDs 50, 52, 54 may be electrically coupled with its one thepads 68, 70, 72 by means of an electrically and thermally conductivebonding material 100 such as a solder, adhesive, coating, film,encapsulant, paste, grease and/or other suitable material. In apreferred embodiment, the LEDs may be electrically coupled and securedto their respective pads using a solder pad on the bottom of the LEDssuch that the solder is not visible from the top. The fabrication of theconnector parts 16, 18, 20 and carrier parts 22, 24, 26 may beaccomplished by stamping, injection molding, cutting, etching, bendingor through other known methods and/or combinations of methods to achievethe desired configurations. For example, the connector parts and/orcarrier parts can be partially metal stamped (e.g., stampedsimultaneously from a single sheet of relevant material), appropriatelybent, and finally fully separated or fully separated following theformation of some or all of the casing.

In some methods of manufacturing the LEDs may be coupled to the pads 68,70, 72 prior to molding and/or assembling the casing 12 about theconnection pads. Alternatively, the LEDs may be coupled to the pads 68,70, 72 after the anode and cathode parts have been partially encasedwithin the casing. The cavity 40 that extends into the casing may beconfigured so that sufficient portions of the pads 68, 70, 72 and pads76, 78, 80 are exposed to receive the LEDs and the associated wirebonds, and to allow the LEDs to emit light out through the cavity 40.

In conventional packages, the smooth surfaces between the lead frame'sanode parts 16, 18, 20 and cathode parts 22, 24, 26 and the upper andlower portions of the casing 12 make reliable adhesion difficult. Thesemating smooth surfaces can reduce the rigidity of the emitter packageand can increase the chances of component failure by separation of thecasing from the lead frame. The smooth surfaces can also allow for aseepage path for moisture to enter the casing. This also result incomponent failure and can reduce the ability of the emitter package tobe used in applications requiring waterproof operation. To increase theadhesion reliability and rigidity and to allow for waterproof operation,one or more of the anode parts 16, 18, 20 and cathode parts 22, 24, 26may further include one or more indentations, through-holes, apertures,extensions, and/or other features that contribute to the stability,integrity and/or robustness of the SMD package. These features may alsoenable the casing 12 and/or fill material 48 to bind better to the leadframe 14, which prevents moisture from infiltrating the device andallows for a waterproof utilization.

As best shown in FIGS. 7 and 9, anode parts 16, 18, 20 and cathode parts22, 24, 26 may include respective through-holes 102, 104, 106, 108, 110,112 that are located generally on the top surface of the lead frame. Asbest shown in FIGS. 7 and 10, the anode and cathode parts may alsocontain features such as V-cuts 114 located adjacent to thethrough-holes. The V-cuts 114 can be on the upper and lower surfaces ofthe anode parts 16, 18, 20 and cathode parts 22, 24, 26. Thethrough-holes 102, 104, 106, 108, 110, 112, V-cuts 114, indentations,and/or other such features of the leads cooperate with the casing and/orfill material, at least in part, to enhance the structural stability andintegrity of the package 10. In some implementations, the casingmaterial and/or fill material extends at least partially into and/orthrough one or more of the through-holes 102, 104, 106, 108, 110, 112formed in the leads to add rigidity. The casing and/or fill material canalso fill the V-cuts to add rigidity and to block seepage of liquids tothe interior of the package 10.

Referring now to FIG. 7, to further enhance the rigidity of the package10 and to increase the reliability of the bond between casing 12 and thelead frame 14, the anodes parts 16, 20 and cathode parts 22, 26 can haveside indentations 115 such that they have a wave shape. When the package10 is fabricated, the casing material fills the indentations with thehardened casing material cooperating with the indentations to hold thecasing 12 to the lead frame. Similarly, anode part 18 and cathode part24 have side tabs 117 that also cooperate with the hardened casing orfill material to hold the casing 12 to the lead frame 14.

FIGS. 11-13 show another embodiment of an emitter package 200 accordingto the present invention that can also be surface mounted. The package200 is similar in most respects to the package 10 shown in FIGS. 1-8,and described above except that thermally conductive bodies 202, 204,206 have been included. The bodies 202, 204, 206 are arranged in thecasing 208 to provide a thermally conductive path from the LEDs to thecasing's lower surface. The bodies can then be further arranged inthermal communication with one or more heat spreaders to efficientlydissipate the heat from the LEDs. The package 200 can be used with manydifferent heat spreaders arranged in many different ways.

The thermally conductive bodies 202, 204, 206, can have many shapes andsizes and can comprise, for example, a rectangular block or a cylinderextending, vertically and at least partially through the casing 208. Inthe embodiment shown, the bodies 202, 204, 206 extend through the casing208 from the surface having the LEDs to the casing's lower surface 212.As best shown in FIG. 11, the bottom surface of conductive body 204 isexposed at the lower surface 212 through an aperture 210 in the lowersurface 212 and disposed substantially flush with the lower surface 212.The bodies 202 and 206 can also be exposed at the bottom surface asshown in FIG. 12. The bottom surfaces of the bodies are arranged in heattransfer relationship with a heat spreader or dissipater 214 carried bya substrate 216 such as printed wiring or a circuit board. Thermallyconductive bodies, given their relatively substantial mass and crosssection area normal to the direction of heat flow, can serve as anefficient heat sink providing a low thermal resistance path (arrows 218)between the heat-generating LEDs carried by the carrier pads and theheat spreader 214. Some heat is also dissipated along the leads (arrow220).

Like the package 10, the package 200 shown in FIGS. 11-13 comprises apreferably dark or black ceramic casing 208 comprising opposed upper andlower surfaces 222, 212, side surfaces 208, 224 and end surfaces 226,228. The SMD 200 carries a lead frame 230 comprising, as before, threeanode parts, three cathode parts. However, as with the above preferredembodiment, it is understood that any number of connection parts,carrier parts and other lead frame portions may be used in a desiredapplication without departing from the scope of the present invention.The chip carrier parts 218 comprise a surface or pad for receiving LEDchips, typically comprising red, green and blue LEDs, other variousother LED color may also be used. As before, the connection partsinclude enlarged wire bond pads positioned in the region adjacent to,but spaced apart from, the chip carrier parts.

As before, the leads are bent orthogonally to extend along and outsideof their respective casing end surfaces, then bent orthogonally again sothat end portions 232, 234, 236, 238, 240, 242 of the leads extend alongthe bottom surface 212 of the casing. The outwardly facing surfaces ofthe end portions 232, 234, 236, 238, 240, 242 of the leads areelectrically connected or bonded to traces or pads on a substrate 216,typically a printed circuit board, using any of a number of well knownconnection techniques. As before, the casing has a cavity 244 thatextends a sufficient depth to expose the pads of the connection partsand carrier parts. The connection parts and carrier parts are preferablymade from an electrically conductive sheet metal or sheet metal alloycut from sheet metal stock by means of punch press operations and thenbent into their final configuration either before or after the formationof the casing about the lead frame.

Each of the LEDs has a pair of electrical terminals or electrodes, thecathodes of which are electrically coupled to the carrier pads while theanodes of the LEDs are coupled, respectively, to the pads of theseparate connection parts by single wire bonds.

With reference now to FIGS. 14-16, some examples of dimensionalcharacteristics of the various components of an SMD 10 or 200 are shown.By way of example and not limitation, the SMD 10 or 200 may have anoverall length of ˜5.50 mm, an overall width of ˜5.50 mm, and a heightof ˜2.50 mm.

With reference to FIG. 17, there is shown in schematic form a portion ofan LED display screen 300, for example, an indoor and/or outdoor screencomprising, in general terms, a driver PCB 302 carrying a large numberof surface-mount devices 304 arranged in rows and columns, each SMDdefining a pixel. The SMDs 304 may comprise devices such as theembodiments shown in FIGS. 1-8, and 11-13. The SMD devices 304 areelectrically connected to traces or pads on the PCB 302 connected torespond to appropriate electrical signal processing and driver circuitry(not shown). As disclosed above, each of the SMDs carries a verticallyoriented, linear array 306 of red, green and blue LEDs. Such a linearorientation of the LEDs has been found to improve color fidelity over awide range of viewing angles.

While several illustrative embodiments of the invention have been shownand described, numerous variations and alternate embodiments will occurto those skilled in the art, such as utilizing the present invention forLED decorative lighting or the like. Such variations and alternateembodiments are contemplated, and can be made without departing from thespirit and scope of the invention as defined in the appended claims.

1. An emitter package, comprising: a casing comprising a cavityextending into the interior of said casing from a top surface of saidcasing; and a lead frame integral to said casing, said lead framecomprising a plurality of electrically conductive carrier parts eachholding at least one of a plurality of light emitting devices, saidlight emitting devices arranged in linear alignment and emitting outsaid cavity, said lead frame also allowing for an electrical signal tobe applied to said light emitting devices through said lead frame,wherein said lead frame further comprises through-holes and V-cuts,wherein said V-cuts are disposed into said lead frame on planes runninggenerally perpendicular to the surface of said lead frame, wherein atleast some of said through-holes intersect with at least some of saidV-cuts, said holes and cuts fitting with said casing; wherein each ofsaid carrier parts further comprises an integral thermally conductivebody extending at least partially through to the bottom of said casing.2. The emitter package of claim 1, wherein said light emitting devicescomprise LEDs, which are adapted to be energized to produce incombination a substantially full range of colors.
 3. The emitter packageof claim 1, wherein said lead frame is arranged to allow for surfacemounting of said package.
 4. The emitter package of claim 1, whereinsaid V-cuts are disposed on both sides of said lead frame.
 5. Theemitter package of claim 1, wherein said lead frame comprises aplurality of electrically conductive cathode parts each having an attachpad for carrying at least one of said light emitting devices, each saidattach pad being electrically coupled to its one of said light emittingdevices, and a corresponding plurality of electrically conductive anodeparts separate from each said cathode part, each of said anode partshaving a connection pad arranged to allow electrical connection to oneof said light emitting devices, wherein said attach pads and connectionpads are arranged to hold light emitting devices in linear alignment. 6.The device of claim 5, wherein each of said light emitters iselectrically coupled to each of said connection pads by a wire bond. 7.The emitter package of claim 1, wherein said lead frame furthercomprises a side indentation.
 8. The emitter package of claim 7, whereinsaid side indentation cooperates with said casing.
 9. The emitterpackage of claim 1, wherein said cavity is at least partially filledwith a fill material.
 10. The emitter package of claim 9, wherein saidthrough-holes and V-cuts are at least partially filled by said fillmaterial.
 11. The emitter package of claim 9, wherein said lead framefurther comprises a side indentation cooperating with said fillmaterial.